Numerical Modeling of Counterflow Diffusion Flames Inhibited by Iron Pentacarbonyl.
Numerical Modeling of Counterflow Diffusion Flames
Inhibited by Iron Pentacarbonyl.
Rumminger, M. D.; Linteris, G. T.
NISTIR 6243; 13 p. October 1999.
Fire Safety Science. Proceedings. Sixth (6th)
International Symposium. International Association for
Fire Safety Science (IAFSS). July 5-9, 1999, Poitiers,
France, International Association for Fire Safety
Science, Boston, MA, Curtat, M., Editor(s), 289-300 pp,
Available from: National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
1-800-553-6847 or 703-605-6000;
ON BOOK SHELF: TH9112.F5626 2000
Order number: PB2000-102626
halon alternatives; diffusion flames; flame inhibition;
iron pentacarbonyl; counterflow flames; extinction
This paper presents the first detailed numerical study
of the extinction of methane-air counterflow diffusion
flames by the super-effective agent iron pentacarbonyl.
Calculations using a gas-phase chemical mechanism
reproduce the magnitude of inhibition for small amounts
of inhibitor in the air, but overpredict the inhibition
effect for larger amounts of inhibitor. Reaction
pathway and reaction flux analyses show that a catalytic
cycle involving FeO, Fe(OH)2, and FeOH is primarily
responsible for catalytic recombination of H atoms which
produces the inhibition, and that a new cycle involving
Fe(OH), FeOOH and Fe(OH)2 has a minor role. Reaction
flux calculations demonstrate that the fractional flux
of H and O atoms through the iron reactions increases as
inhibitor concentration increases, but eventually the
fractional fluxes level off. Saturation of the
catalytic cycles can partially explain the diminishing
effect of the inhibitor at high inhibitor loading shown
in both the calculated and experimental results. Flame
structure calculations are used to determine the reasons
for stronger inhibition for air-side addition of the
inhibitor than for fuel-side. Simulations using a
idealized inhibitor confirm the important role of
transport in inhibition of counterflow diffusion flames.